Tuesday 20 March 2012 15.53 EDT
First published on Tuesday 20 March 2012 15.53 EDT

Boris Johnson has widened his lead over Ken Livingstone in the battle to become the next mayor of London on 3 May, according to a YouGov poll published to mark the first day of the official election campaign.

The Conservative mayoral candidate and incumbent mayor is eight percentage points ahead, up from a slender margin of just two percentage points in a previous YouGov poll five weeks ago, which cast the race as neck and neck.

The positive rating for Johnson came on a day that his campaign tactics came under fire after it emerged his team had rerouted the official City Hall Twitter account, @MayorofLondon to @BorisJohnson.

The latest YouGov poll shows a drop in perceptions of Livingstone's qualities, suggesting that the intensifying of Johnson's campaign, in which he has repeatedly attacked Livingstone's former mayoral record in negative contrast to his own, is beginning to pay dividends, at a time when the Labour candidate has been mired by criticisms over his personal tax arrangements.

The survey of 1,227 Londoners puts Johnson at 54% to Livingstone's 46% if voters had to choose between the two candidates at the election, which is fought under the supplementary vote system.

Johnson leads by 49% to Livingstone's 41%. Brian Paddick, the Liberal Democrat mayoral candidate, who has stepped up his campaign in recent weeks, will be disappointed to see he has dropped to just 5%, down from 6% in the February poll.

Livingstone has seen a decline in those who see him as a candidate who "sticks to what he believes in" (from 40% to 34%), and as someone in touch with the concerns of ordinary Londoners (down 5 percentage points from 37% to 32%. However, fewer respondents this time think Johnson is in touch with ordinary Londoners, down from 15% to just 13%.

Anthony Wells, associate director of YouGov's political research, said: "Our last poll came when Ken had been making the running with his pledge to cut fares. Since then Boris has campaigned more actively, while Ken has had a troubled month facing accusations over his personal tax affairs.

"Consequently our figures show a significant shift towards Boris in who people think has the better record as mayor, and a drop in perceptions of Ken's personal qualities. Boris starts the official race with a small lead, but there are six weeks still to go."

The two rivals hit the campaign trail on Tuesday, with Livingstone in Kilburn, pushing his promise of a 7% fares cut to Londoners. Johnson was out courting the vote in Bexley as he highlighted projects which will secure up to 200,000 jobs in the next four-year term.

He said the coalition government's agreement to hand him powers to invest £3bn in housing would allow him to create 104,000 jobs, while 32,300 would result from investment in transport, 5,500 in redevelopment of the Greenwich Peninsula and Royal Docks and a further 59,500 through a variety of initiatives he is planning.

"What we are trying to get over is that this is a historic choice for Londoners," he said. "They can either go forward with a programme that invests in our city that keeps directing hard earned taxpayers' cash at the transport housing investments that will take London forward or we can go back a wasteful and mismanaged approach to the government I'm afraid you saw under Ken Livingstone when huge sums were squandered on this of no conceivable benefit to London."

While the YouGov poll put tackling crime and improving transport at the top of people's concerns, a separate survey conducted by Ipsos Mori for the BBC suggests jobs, growth and the economy are the issue of most concern to Londoners.

The Ipsos Mori survey put Johnson and Livingstone at 27% each when it comes to who is most trusted with the economy.

The BBC poll showed widespread support for Livingstone's fares, with 82% backing the plan. However, when asked who had the best policies on transport, they gave Johnson a five-point lead on 36% compared with Livingstone's 31%.

Livingstone said: "After years of rising train, bus and tube fares under the Tory Mayor this poll shows Londoners want a Mayor who will cut the fares and make them better off. It's remarkable that with 82% of Londoners saying they want a fares cut, Boris Johnson wants to continue his policy of above inflation fare increases. If I'm elected on May 3rd I will cut the fares, saving Londoners £1000 on average over four years."

Johnson said he would continue to champion the London Living Wage, which is set at £8.30, by encouraging firms to sign up. "The Living Wage delivers benefits not just for workers, not just for people on low incomes, it delivers benefits for firms that have the good sense to pay it because it creates loyalty it creates commitment and it actually saves on the cost of workforce turnover," he told the Guardian.